Combustion of fossil fuels is reported to be a major cause of the increased concentration of CO2 in the atmosphere. Although research is ongoing to improve energy efficiency and to substitute low-carbon fuels to combat this problem, these methods will likely be insufficient to limit the growth of atmospheric CO2 concentrations to an acceptable level. New technologies to separate and sequester CO2 that is generated are therefore being pursued.
The Department of Energy has reported that existing CO2 capture technologies are not cost-effective when considered in the context of large power plants. The net electricity produced from existing plants would be significantly reduced upon implementation of any of these CO2 capture technologies, since a high percentage of the power generated by the plant would have to be used to capture and compress the CO2.
For example, some technologies utilize various sorbents to sequester CO2 from power plant flue gas via chemical reaction and conversion. This method for the capture of CO2 involves a reaction that can be exothermic. Thus, although CO2 capture is achieved, a new problem arises in the form of a need for cooling the system to keep the absorber temperature in a desired range (e.g., below about 140° F. to 150° F.). Typically, this heat could be removed through the use of cooling water. Additionally, after use, the sorbents may require regeneration for reuse, which requires addition of heat, typically supplied by borrowing low pressure (about 30-50 psig) steam from the steam cycle of the power plant. Accordingly, the overall efficiency of a power plant that includes this type of CO2 capture technology may be diminished by as much as 10 to 15% compared to that of a power plant without any CO2 capture technology in place.
Therefore, it would be beneficial to develop a more efficient CO2 capture method. Specifically, it would be beneficial to develop a new method by which heat generated in the CO2 capture process could be used to generate power, and thus offset the parasitic energy load associated with traditional CO2 capture technologies.